2 April 2019

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Data

The seals data set from the ggplot2 R package consists of

##       lat            long          delta_long        delta_lat       
##  Min.   :29.7   Min.   :-172.8   Min.   :-2.0671   Min.   :-0.45794  
##  1st Qu.:34.7   1st Qu.:-159.8   1st Qu.:-0.8222   1st Qu.: 0.01162  
##  Median :39.7   Median :-145.8   Median :-0.5818   Median : 0.12571  
##  Mean   :39.7   Mean   :-145.8   Mean   :-0.5633   Mean   : 0.14145  
##  3rd Qu.:44.7   3rd Qu.:-131.8   3rd Qu.:-0.3168   3rd Qu.: 0.24642  
##  Max.   :49.7   Max.   :-118.8   Max.   : 0.2578   Max.   : 0.76436

Basically it's the vector field representation of seal movements in the Pacific Ocean.

  • The long and lat variables represent the x and y coordinates of a grid where the measurements are taken.
  • The delta_long and delta_lat variables represent the x and y components of the displacement vector.

Vector field

Countour plot

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The magnitude of the displacement is color-coded on the longitude-latitude grid with added contour lines.

Overall the displacement increase going towards the south-east corner of the grid.

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Radar plot

Mean displacement for fixed longitude and latitude. Colors code the mean longitude and latitude components of the mean displacement.

Notice from the sign of the colors that the movement go from 45 to 30 degrees of latitude, and from -120 to -180 degrees of longitude. On the latitude the displacement magnitude increase linearly, while there is an increase/decrease around -135 degrees on the longitude.